The present invention relates to the field of shock testing for vessels. In particular it relates to a method for testing the ability of vessels to withstand non-contact underwater explosions.
The ability to withstand the effects of non-contact underwater explosions (UNDEX) is an important aspect of the design of modern warships. To demonstrate that a warship structure and equipment are designed and built to the required standard, it is common for the entire warship to be shock tested by detonating controlled explosive charges in close proximity to the vessel. The resulting response of the vessel, its equipment and any ensuing damage is then monitored.
However, shock testing of a vessel can be costly. It requires the use of explosively licensed ranges and can tie up the warship for a significant period due to the transit time to the range and the time spent once there.
Further, the fact it is an operation involving explosives, carries with it significant safety implications both for the trials teams and the vessel under test.
It is an object of the present invention to provide a method and apparatus for underwater shock testing which is safer than current techniques. Furthermore, the present invention aims to provide a technique that does not require a vessel to be transported to a range and which can be rapidly carried out, with a short turnaround time between tests.
Further objects include providing a technique that is more environmentally acceptable than those involving the use of explosives and less likely to damage the vessel being studied. This would allow new types of test. For instance, tests configured directly below a warship""s keel cannot currently be carried out as conventional techniques would cause damage.
According to the present invention, there is provided a method of shock testing ships, submarines, underwater equipment and/or model specimens in which an array of synchronised and phased seismic airguns is used to provide a shock wave which simulates the shock wave produced by an underwater explosive.
Preferably, the characteristics of an explosive shock wave are matched with a compound shock pulse from several guns, specifically matching peak pressure, decay constant and energy flux density.
The shock testing of the ship may take place immediately below the keel of the ship, submarine, underwater equipment and/or model specimen.
Most preferably, the release of high pressure air simulates an explosive shock wave.
The method of shock testing may be as herein described and illustrated in the accompanying drawings.
According to a second aspect of the present invention, there is provided apparatus for shock testing ships, submarines underwater equipment and/or model specimens comprising an array of synchronised and phased seismic airguns which produces a shock wave which simulates the shock wave produced by an underwater explosive.
Preferably, the characteristics of an explosive shock wave are matched with a compound shock pulse from several guns, specifically matching peak pressure, decay constant and energy flux density.
The array of synchronised and phased seismic airguns may be positioned immediately below the keel of the ship, submarine, underwater equipment and/or model specimen.
Most preferably, the release of high pressure air simulates an explosive shock wave.
Preferably, there is provided a method whereby an impulsive load may be supplied to a vessel, ship, model or specimen to simulate operational loadings such as slamming.
Preferably, there is provided a method whereby a dynamic broadband excitation may be applied to modally characterise the structure and determine transfer functions from the fluid domain to parts, structures, equipment and systems within the ship, submarine or vessel.